Search results for "HV"
showing 10 items of 353 documents
A new approach to partial discharge detection under DC voltage
2018
The continuing development of HVDC power transmission systems presents many problems related to evaluation of the reliability of power system assets [1]-[5]. In this context the identification of insulation defects plays a key role in preventing unexpected failures of electrical components. Partial discharge (PD) measurement is a useful approach to assessing the condition of HV power apparatus and cables. Such measurements are also widely employed for HVAC systems. The inception mechanisms of PD in AC systems are well-known, and measurements are usually performed following the IEC 60270 standard [6]. PD measurements under DC voltage present complexities related to the nature of the phenomen…
The Perpetrator's mise-en-scene: Language, Body, and Memory in the Cambodian Genocide
2018
Rithy Panh's film S-21. The Khmer Rouge Killing Machine (2003) was the result of a three-year shooting period in the Khmer Rouge centre of torture where perpetrators and victims exchanged experiences and re-enacted scenes from the past under the gaze of the filmmaker's camera. Yet, a crucial testimony was missing in that puzzle: the voice of the prison's director, Kaing Guek Eav, comrade Duch. When the Extraordinary Chambers in the Courts of Cambodia (ECCC) were finally established in Phnom Penh to judge the master criminals of Democratic Kampuchea, the first to be indicted was this desk criminal. The film Duch, Master of the Forges of Hell (R. Panh, 2011) deploys a new confrontation – an a…
The effect of the axial heat transfer on space charge accumulation phenomena in HVDC cables
2020
To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating …
Etude numérique d'équations aux dérivées partielles non linéaires et dispersives
2011
Numerical analysis becomes a powerful resource in the study of partial differential equations (PDEs), allowing to illustrate existing theorems and find conjectures. By using sophisticated methods, questions which seem inaccessible before, like rapid oscillations or blow-up of solutions can be addressed in an approached way. Rapid oscillations in solutions are observed in dispersive PDEs without dissipation where solutions of the corresponding PDEs without dispersion present shocks. To solve numerically these oscillations, the use of efficient methods without using artificial numerical dissipation is necessary, in particular in the study of PDEs in some dimensions, done in this work. As stud…
Electricity demand management by optimising the use of HVAC and HWS through AMI
2017
The consumption of electricity is increasing with consistent increase in demand of electricity. Advance metering infrastructure (AMI) is a part of energy management system (EMS) that can pro-actively control the consumption of electricity by engaging with utilities for demand management in real-time. The analysis of the electricity consumption pattern of an Australian house is conducted in this study. The investigation reveals that Heat Ventilation Air conditioning (HVAC) and Hot Water System (HWS) consume approximately 50% of the total electricity consumption. Optimised utilization of these two systems efficiently using AMI can help in reduction of electricity consumption. The study also i…
Statistical analysis techniques for Partial Discharges measurement under DC voltage
2022
Partial discharges (PD) phenomenon for HVAC (High-Voltage-Alternating-Current) systems has already been widely studied in literature and from this it has been possible to produce a regulatory document that provides indications for description and identification of the different types of discharges. However, the growing diffusion of HVDC (High-Voltage-Direct-Current) systems makes necessary the development of analysis techniques also for DC case. In this paper data obtained from PD measurement under DC voltage were analyzed through the time-frequency map combined with a density-based clustering algorithm. The results show that, with this approach, it's possible to perform a noise rejection a…
On critical behaviour in generalized Kadomtsev-Petviashvili equations
2016
International audience; An asymptotic description of the formation of dispersive shock waves in solutions to the generalized Kadomtsev–Petviashvili (KP) equation is conjectured. The asymptotic description based on a multiscales expansion is given in terms of a special solution to an ordinary differential equation of the Painlevé I hierarchy. Several examples are discussed numerically to provide strong evidence for the validity of the conjecture. The numerical study of the long time behaviour of these examples indicates persistence of dispersive shock waves in solutions to the (subcritical) KP equations, while in the supercritical KP equations a blow-up occurs after the formation of the disp…
Time Evolution of Partial Discharges in a Dielectric Subjected to the DC Periodic Voltage
2022
Partial discharge (PD) detection can be considered one of the most useful tools for assessing the insulation conditions of the power apparatus in high-voltage systems. Under AC conditions, this analysis is widely employed in online and offline tests, such as type tests or commissioning, and can be carried out by applying the phase-resolved PD (PRPD) method, since the patterns can give information about the defect classification. Under DC voltages, the classic pattern recognition method cannot be performed, and the measurements show complexities related to the nature of the phenomena. For this reason, to date, a standard for PD measurements under DC does not exist. In previous papers, a new …
The Hamilton–Jacobi Equation
2001
We already know that canonical transformations are useful for solving mechanical problems. We now want to look for a canonical transformation that transforms the 2N coordinates (q i , p i ) to 2N constant values (Q i , P i ), e.g., to the 2N initial values \((q_{i}^{0},p_{i}^{0})\) at time t = 0. Then the problem would be solved, q = q(q0, p0, t), p = p(q0, p0, t).